On Thu, 7 Jul 2011, Pekka Enberg wrote: > On Wed, 6 Jul 2011, Pekka Enberg wrote: >>> Why does the allocator need to know about address boundaries? Why >>> isn't it enough to make the page allocator and reclaim policies favor >>> using >>> memory from lower addresses as aggressively as possible? That'd mean >>> we'd favor the first memory banks and could keep the remaining ones >>> powered off as much as possible. >>> >>> IOW, why do we need to support scenarios such as this: >>> >>> bank 0 bank 1 bank 2 bank3 >>> | online | offline | online | offline | >> > On Wed, 6 Jul 2011, david@xxxxxxx wrote: >> I believe that there are memory allocations that cannot be moved after they >> are made (think about regions allocated to DMA from hardware where the >> hardware has already been given the address space to DMA into) >> >> As a result, you may not be able to take bank 2 offline, so your option is >> to either leave banks 0-2 all online, or support emptying bank 1 and taking >> it offline. > > But drivers allocate DMA memory for hardware during module load and stay > pinned there until the driver is unloaded, no? So in practice DMA buffers are > going to be in banks 0-1? that depends on when the device was initialized. it is common for them to be in the beginning, but with hotplug, who knows. David Lang _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
